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United States Patent |
5,789,453
|
Detterman
|
August 4, 1998
|
Medium density chlorinated polyvinyl chloride foam and process for
preparing
Abstract
The present invention relates to a medium density chlorinated polyvinyl
chloride foam and the method of preparing such a foam using a blend of
chemical blowing agents. The foam having a specific gravity in the range
of about 0.3 to about 1.5 comprises chlorinated polyvinyl chloride, a
blend of decomposition type blowing agents, a tin stabilizer, a optional
impact modifier and a optional high molecular weight process aid.
Inventors:
|
Detterman; Robert Edwin (Medina, OH)
|
Assignee:
|
The B. F. Goodrich Company (Richfield, OH)
|
Appl. No.:
|
831671 |
Filed:
|
April 10, 1997 |
Current U.S. Class: |
521/92; 521/81; 521/93; 521/94; 521/99; 521/134; 521/139; 521/140; 521/145 |
Intern'l Class: |
C08J 009/08 |
Field of Search: |
521/79,81,92,93,94,134,139,140,145
|
References Cited
U.S. Patent Documents
4360602 | Nov., 1982 | Nehmey et al. | 521/145.
|
4370286 | Jan., 1983 | Nehmey et al. | 521/145.
|
4383048 | May., 1983 | Hall et al. | 521/145.
|
4413065 | Nov., 1983 | Hall et al. | 521/145.
|
4980383 | Dec., 1990 | Shimazu et al. | 521/145.
|
Primary Examiner: Foelak; Morton
Attorney, Agent or Firm: Odar; Helen A., Dureska; David P., Laferty; Samuel B.
Claims
We claim:
1. A medium density foam having a specific gravity in the range of 0.3 to
1.5 having been foamed from a composition comprising chlorinated polyvinyl
chloride, decomposition type blowing agent(s) or blends thereof, a tin
stabilizer, and an impact modifier, wherein said decomposition blowing
agent comprises a blend of bicarbonate and azodicarbonamide blowing agent.
2. A medium density foam according claim 1, wherein said bicarbonate
blowing agent comprises from about 30 to about 60% of the decomposition
blowing agent.
3. A medium density foam according to claim 2, wherein said bicarbonate
blowing agent comprises about 50% of the decomposition blowing agent.
4. A medium density foam according to claim 1, wherein said
azodicarbonamide blowing agent comprising from about 40 to about 70% of
the decomposition type blowing agent.
5. A medium density foam according to claim 1 wherein said impact modifier
is chosen from the group consisting essentially of acrylic impact
modifiers, MBS impact modifiers, ABS impact modifiers, silicon
rubber/acrylic copolymer impact modifiers and chlorinated polyethylene
impact modifier.
6. A medium density foam according to claim 5, wherein said impact modifier
is an acrylic impact modifier.
7. A medium density foam according to claim 5, wherein said impact modifier
is found in the range of about 0.1 to about 10 parts per 100 parts of
CPVC.
8. A medium density foam according to claim 7, wherein 6 parts of impact
modifier are used.
9. A medium density foam according to claim 1, further comprising a high
molecular process aid.
10. A medium density foam according to claim 1, wherein said chlorinated
polyvinyl chloride has 67% chlorine, 0.68 inherent viscosity and a fused
density of 1.5757 grams/cc.
11. A medium density foam according to claim 1, the composition further
comprising an optional costabilizer.
Description
FIELD OF INVENTION
This invention relates to a medium density chlorinated polyvinyl chloride
foam composition. In particular, the invention relates to a medium density
foam composition having a substantially closed cell spherical structure
and a specific gravity of approximately 0.3 to approximately 1.5, having
thermal stability and improved impact resistance as compared to other
medium density foams. Furthermore, the invention relates to the method of
making such a medium density foamed composition using a blend of blowing
agents, wherein such blend provides for a balance of properties, better
than either blowing agent by itself.
BACKGROUND OF THE INVENTION
Foamed thermoplastic products are currently made using either physical or
chemical blowing agents. Physical blowing agents are gases or liquids at
temperatures below the processing temperatures of the thermoplastics.
Generally, with physical blowing agents it is difficult to obtain uniform
cell distribution due to the lack of uniformity of application of the
physical blowing agent because of the difficulty in mixing the physical
blowing agent with the highly viscous polymer melt. Furthermore, the
addition of large amounts of physical blowing agents which are dissolved
into a polymer dramatically decreases the polymer glass transition
temperature making a highly plasticized mixture which is processed at
lower temperatures thus allowing the processor to maintain the thermal
stability of the polymer. Physical blowing agents are generally used in
the formation of low density foams which generally have a specific gravity
of less than 0.1.
Chemical blowing agents decompose or interact upon being heated to a
temperature below the processing temperature of the thermoplastic and
liberate a gaseous product in order to expand the thermoplastic. Chemical
blowing agents by themselves are not generally used in low density foams
because they are expensive and produce a limited reduction in density by
themselves.
Foams made from chlorinated polyvinyl chloride, in particular, retain many
of the properties of chlorinated polyvinyl chloride polymers such as heat
resistance, chemical resistance, and weathering resistance, as compared to
other thermoplastic polymers. Therefore, the foam of a chlorinated
polyvinyl chloride can be used in a wide variety of applications.
For example, Adachi, et. al., in U.S. Pat. No. 4,165,415 discloses a method
for preparing both low and medium density foams of CPVC. The method
comprises impregnating a chlorinated polymer of vinyl chloride with a
foaming agent consisting essentially of a lower aliphatic monohydric
alcohol having between 1 to 5 carbon atoms. The foaming agent is
considered a physical blowing agent. The mixture is then heated to a
temperature and for a time sufficient to cause the mixture to foam in a
closed mold.
U.S. Pat. No. 4,772,637 to Kimura, et. al., describes the method of
preparing pre-expanded particles of CPVC containing a large amount of
inorganic materials . The CPVC, inorganic materials and a solvent are
kneaded to form a gel. The kneaded mixture is pelletized and a physical
blowing agent is impregnated into the pellets. The pellets are then
pre-expanded. The pre-expanded particles are then placed in a mold and
heated with a heating source to expand and fill the mold in order to
obtain a foamed article.
The abstract of Japanese Patent No. 51024667 describes a heat and flame
resistant CPVC resin having a chlorine content of 63-69% in a nitrobenzene
solution. An organic foaming agent such as azodicarbonamide, or
dinitrosopentamethylene tetramine along with processing agents such as
heat stabilizers, and lubricants were added. These ingredients were then
foamed.
The abstract of Japanese Patent No. 5148381 discloses a composition which
is foamed to give a five (5) millimeter cellular sheet with a density
(sic) of 0.74. The composition is obtained by compounding dibutyl tin
maleate, dioctyl tin maleate, a chemical foaming agent and an acrylic
processing aid with a vinyl chloride polymer. The chemical foaming agent
can be an azo compound, an azide compound, a nitroso compound, and/or a
sulpho-hydrazide compound. The acrylic processing aid is a homopolymer or
copolymer of methyl methacrylate, ethyl methacrylate, butyl methacrylate,
copolymers of alkyarylates, and so forth.
German Patent Disclosure Publication No. DE-OS 2302521 describes a process
for the preparation of a flexible thermoplastic foamed material. The
patent describes heating a mixture of chlorinated polyethylene and
chlorinated polyvinyl chloride and a blowing agent in a closed space at a
temperature above the softening point of the chlorinated polymer and above
the decomposition temperature of the blowing agent. The blowing agent that
can be used in the process is azodicarbonamide.
U.S. Pat. No. 4,383,048 to Hall, et.al., discloses the process of making
low density chlorinated polyvinyl chloride foam having a density of 0.32
grams/cubic centimeter or less. The low density foam that is produced that
has a substantially closed cell structure, low thermal conductivity and
excellent thermal stability without the substantial amounts of stabilizer
required when azodicarbonamide is used as the nucleating agent. The foam
is produced using a primary blowing agent which could be gaseous nitrogen
and an alkali metal borohydride in conjunction with a proton donor
activator as the nucleating agent.
A chlorinated polyvinyl chloride composition to be foamed is described in
U.S. Pat. No. 4,370,286. The composition comprises a chlorinated polyvinyl
chloride resin containing at least sixty (60%) percent chlorine, an
effective amount of a blowing agent, an effective amount of a nucleating
agent, a processing aid selected from copolymers of styrene and
unsaturated nitrile containing more than fifty percent (50%) of styrene
and ten to forty percent (10-40%) of nitrile. The foam formed from the
composition is a low density foam.
U.S. patent application No. 08/580,563, filed Dec. 29, 1995, discloses a
medium density chlorinated polyvinyl chloride foam composition comprising
a chlorinated polyvinyl chloride polymer containing at least sixty percent
(60%) chlorine by weight, a nitrogen containing decomposition type blowing
agent, a tin stabilizer, a costabilizer and a high molecular weight
process aid. However, this medium density foam lacks good impact
resistance properties. Comparatively, the present invention has improved
impact properties or at a minimum displays a less brittle mode of failure
from those compositions set forth in U.S. patent application No.
08/580,563. Furthermore, one of the components of blend of the blowing
agents used in this application acts as a costabilizer for the CPVC
itself, precluding the need for a separate costabilizer.
Thus, there currently exists a need for a composition to form a medium
density chlorinated polyvinyl chloride foam in which such foam has good
dynamic thermal stability and color stability and improved impact
resistance. In particular, a need exists for a medium density CPVC foam
having chemical resistance, good weathering characteristics, and high
service temperature or Vicat softening temperature.
SUMMARY OF THE INVENTION
The present invention comprises a novel medium density chlorinated
polyvinyl chloride foam composition comprising a chlorinated polyvinyl
chloride polymer containing at least sixty percent (60%) chlorine by
weight, a blend of decomposition type blowing agent(s), a tin stabilizer,
a optional impact modifier, and a optional high molecular weight process
aid.
Preferably, the medium density chlorinated polyvinyl chloride foamed
composition further includes an effective amount of lubricant(s).
The present invention also comprises the method of forming a medium density
chlorinated polyvinyl chloride foam.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a bar graph setting forth the Dynamic Thermal Stability (DTS)
results of Table 3.
FIG. 2 shows the results of the DTS experiments carried out for the
compositions in Table 10 in bar graph form.
FIG. 3 is a bar graph showing the DTS of the experimental compounds set
forth in Table 12.
FIG. 4 is a bar graph showing the DTS of Table 14.
FIG. 5 compares the VHIT test of various experiments in the invention with
a comparative recipe from U.S. patent application No. 08/580,563.
FIG. 6 compares the affect of a blend of blowing agents on PVC and CPVC,
and CPVC with a costabilizer.
FIG. 7 is an electron micrograph at 15.times. magnification using a
Scanning Electron Microscope (SEM) of a CPVC foamed by 100%
azodicarbonamide blowing agent.
FIG. 8 is an electron micrograph at 15.times. magnification using a SEM
illustrating a foamed CPVC sample using a 80/20 blend of blowing agent
wherein azodicarbonamide is the major portion of the blowing agent.
FIG. 9 is an electron micrograph at 15.times. magnification using a SEM
illustrating a foamed CPVC sample using a 60/40 blend of blowing agent
wherein azodicarbonamide is the major portion of the blowing agent.
FIG. 10 is an electron micrograph at 15.times. magnification using a SEM
illustrating a foamed CPVC sample blown using a 40/60 blend of blowing
agent wherein azodicarbonamide is the minor portion of the blowing agent.
FIG. 11 is an electron micrograph at 15.times. magnification using a SEM
illustrating a section of a foamed CPVC sample blown using a 20/80 blend
of blowing agent wherein azodicarbonamide is the minor portion of the
blowing agent.
FIG. 12 an electron micrograph at 15.times. magnification using a SEM
illustrating a section of a foamed CPVC foamed by 100% sodium bicarbonate
blowing agent.
DETAILED DESCRIPTION
The chlorinated polyvinyl chloride medium density foams of the present
invention are prepared from compositions comprising chlorinated polyvinyl
chloride polymer, a blend of two chemical blowing agents, a tin
stabilizer, a optional impact modifier and a optional high molecular
process aid. Other ingredients generally added to chlorinated polyvinyl
chloride compositions, such as, for example, but not limited to
lubricants, processing aids, fillers and pigments may also be included in
the compositions. The medium density foams of the present invention are
illustrated in FIGS. A-F. As seen in those figures, the medium density
foams of the present invention are characterized as having a substantially
closed cell spherical structure, a cell size substantially less than 500
microns, a specific gravity in the range of approximately 0.3 to
approximately 1.5. The foam may have a densified skin if the foam is free
blown. If found at all, the densified skin is very thin, generally ranging
from approximately 1 mils to approximately 10 mils.
The chlorinated polyvinyl chloride polymer (CPVC) used in producing the
medium density foam of the present invention refers to products obtained
by post chlorinating a polymer of vinyl chloride (PVC). Vinyl chloride
polymers include both homopolymers and copolymers of vinyl chloride,
having a chlorine content up to 56.7%. Vinyl chloride polymers may be
formed by mass, suspension or emulsion polymerization. Most preferably,
the vinyl chloride polymers are formed by mass polymerization.
CPVC is obtained by chlorinating homoploymers or copolymers containing less
than fifty percent (50%) by weight of one or more copolymerizable
comonomers. Preferably, comonomers are not used. However, if used,
suitable comonomers include acrylic and methacrylic acids; esters of
acrylic and methacrylic acid wherein the ester portion has from 1 to 12
carbons; hydroxyalkyl esters of acrylic and methacrylic acid (for example
hydroxymethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl
methacrylate and the like); glycidyl ester of acrylic and methacrylic acid
(for example glycidyl acrylate, glycidyl methacrylate and the like);
alpha, beta-unsaturated dicarboxylic acids and their anhydrides (for
example maleic acid, fumaric acid, itaconic acid and the like); acrylamide
and methacrylamide; acrylonitrile and methacrylonitrile; maleimides;
olefins (for example ethylene, propylene, isobutylene, hexene and the
like); vinylidene halide; vinyl esters; vinyl ethers; crosslinking
monomers (for example, diallyl phthalate, ethylene glycol dimethacrylate,
methylene bisacrylamide, divinyl ether, allyl silanes and the like).
Any post chlorination processes can be used to form CPVC polymer having
more than fifty-seven percent (57%) by weight chlorine based upon the
total weight of the polymer. Preferably, the CPVC polymer has a chlorine
content in the range of about sixty percent (60%) to about seventy four
percent (74%) by weight based upon the total weight of the polymer. The
post chlorination processes which can be used include any commercial
process or the like such as solution process, mass polymerization,
fluidized bed process, water slurry process, thermal process or liquid
chlorine process. In as much as the post chlorination processes are known
to the art as well as the literature, they will not be discussed in detail
here. Rather reference is hereby made to U.S. Pat. Nos. 2,996,049;
3,100,762; 4,412,898 and 5,216,088 which are hereby fully incorporated by
reference as to the method of forming CPVC by post chlorinating PVC. A
preferred process in forming the CPVC from the PVC is the aqueous
suspension process disclosed in U.S. Pat. No. 4,412,898. However, the most
preferred process to form CPVC is from a PVC made from a mass process.
In addition, blends of various CPVC resins can also be used. In those
instances, the CPVC resin can be blended with another CPVC resin in an
amount of other resin of about 1% to about 50%. Furthermore, the CPVC can
be blended with PVC. The amount of PVC to be included ranges from about 1
to 50%.
The CPVC used in the invention desirably will have a fused density in the
range of approximately 1.45 to 1.65 grams /cubic centimeter at 25.degree.
Centigrade, an inherent viscosity (I.V.) in the range of about 0.41 to
about 1.15 and a chlorine content of at least sixty percent (60%). The
preferred fused density of the CPVC is in the range of about 1.5 to about
1.6 grams/cubic centimeter. The preferred inherent viscosity is in the
range of about 0.5 to about 0.7. The preferred chlorine content of the
CPVC is about 67% to about 68.5%. The most preferred chlorine content is
67%, with a 0.68 I.V. and a fused density of 1.5737 grams/cubic
centimeter. Examples of suitable CPVC to use in forming the medium density
foam of the instant invention include TempRite.RTM. 677.times.670 CPVC,
TempRite.RTM. 637.times.670 CPVC and TempRite.RTM. 639.times.683 CPVC, all
available from The B. F. Goodrich Company. "TempRite" is a registered
trademark of The B. F. Goodrich Company. The preferred resins are
TempRite.RTM. 687.times.563 CPVC and TempRite.RTM. 637.times.670 CPVC. The
most preferred CPVC resin is TempRite.RTM. 637.times.670 CPVC.
The chemical blowing agents which are useful for foaming CPVC include
blends of acid scavengers which generate gas with a nucleating blowing
agent. The acid scavenger which also generates gas acts as a possible
costabilizer for the CPVC. The acid scavenger must be able to react with
hydrogen chloride which evolves during the degradation of the CPVC
polymer. An example of an acid scavenger which generates gas is a
bicarbonate blowing agent. An example of nucleating agent is
azodicarbonamide.
Examples of bicarbonate blowing agents include ammonium bicarbonate and
sodium bicarbonate. A further discussion of these types of blowing agents
can be found in the "Handbook of Polymeric Foams and Foam Technology" by
Klempner, et.al., pages 380-381, incorporated herein by reference in their
entirety. Examples of possible bicarbonate decomposition type blowing
agents include Hydrocerol BIS and Hydrocerol BIF, available from
Boehringer Ingelheim; Safoam P and Safoam FP, both available from the
Balchem Corporation. In CPVC, the bicarbonate blowing agent releases a
great volume of carbon dioxide. The rate of gas release is very fast. The
use of the bicarbonate blowing agent improves the thermal stability of the
compound. However, the processability of such a compound is poor and cell
structure of the foam produced very coarse. The foamed material, however,
does have excellent color retention.
The bicarbonate chemical blowing agent is blended with azodicarbonamide, a
nitrogen containing decomposition type blowing agent. Azodicarbonamide has
excellent blowing properties, promotes fine cell structure, evolves large
amounts of gas when decomposed, when used alone. In addition, the
azodicarbonamide behaves as a slower decomposer than the bicarbonate
decomposition blowing agent on a volume per volume comparison. The
preferred azodicarbonamides are Unicell D-200 and Unicell D-400, both
available from Jong. The most preferred azodicarbonamide is Unicell D-200.
Furthermore, the azodicarbonamide by itself has an activation temperature
in the range of about 185.degree. C. to about 205.degree. C., which raises
the decomposition temperature of the blend of chemical blowing agents
closer to the processing temperature of CPVC which is generally in the
range of about 190.degree. C. to about 220.degree. C. The bicarbonate
decomposition type blowing agent alone has an activation temperature
around 120.degree. C. It is believed that blending a bicarbonate chemical
blowing agent with an azodicarbonamide blowing agent gives the foamed CPVC
better thermal stability, color stability, and much better process
control, than either agent by itself while maintaining the properties of
the medium density foam. Furthermore, the foam formed by the blend has
smaller cell structures than if solely the bicarbonate decompostion type
blowing agent was used. Preferably the bicarbonate decomposition type
blowing agent comprises from about 30 to about 60% of the decomposition
type blowing agent mixture, while the azodicarbonamide comprises from
about 70 to about 40% of the decomposition type blowing agent. Most
preferably, the blend is a 50:50 ratio of the two agents. An example of a
commercially available blend of a bicarbonate blowing agent and
azodicarbonarnide is Exercol 232 from B. I. Chemicals, Inc. It is believed
that the Exercol 232 comprises approximately 79% sodium bicarbonate and
approximately 21% azodicarbonamide. Additional azodicarbonamide is added
to this commercial blend in the instant case. It is believed that as the
azodicarbonamide level approaches the lower limit of about 40%, the
processing melt flow stability of the blend is still maintained. However,
as more of the azodicarbonamide is added into the decomposition type
blowing agent mixture, the stability of the foamed CPVC will be
diminished. Therefore, the optimum blend requires a balancing of benefits
and detriment to the polymer itself. The range for the two components of
the decomposition type blowing mixture provides high volume of gas
release, and fast gas release reactions. The blend provides a positive
effect on the thermal stability as compared to either of the two blowing
agents in the blend. In addition, the blend provides CPVC foam which is
easily processed and does not appear to have the cell structure
significantly changed. Furthermore, the foam has good color retention.
The tin stabilizer used in the present invention can be any stabilizer
containing tin. Suitable stabilizers include tin salts of monocarboxylic
acids such as stannous maleate. Additionally, organo-tin stabilizers such
as dialkyl tin mercaptides, carboxylates, and thiazoles can be used.
Examples of such organo-tin stabilizers include without limitation:
dibutyltin dilaurate, dibutyltin maleate, di(n-octyl) tin maleate,
dibutyltin bis(lauryl mercaptide), dibutyltin, S,S-bis(isooctyl
thioglycoate), dibutyltin .beta.-mercaptoproprionate, di-n-octyltin
S,S-bis(isooctyl thioglycolate), and di-n-octyltin
.beta.-mercaptoproprionate. Usually from about 1 to about 5 parts by
weight of stabilizer per 100 parts by weight of chlorinated polyvinyl
chloride is used in the composition. Most preferably, the composition uses
3.5 parts of butyl tin thioglycolate per 100 parts of CPVC polys. Examples
of commercially available tin stabilizers include Mark 292-S from Witco
Chemical and Thermolite 31HF from Elf Atochem.
In addition to the tin stabilizer, the foamable composition may optionally
contain a costabilizer. However, the costabilizer is not a necessary
ingredient to make the medium density CPVC foam of the instant invention.
In particular, when using the acid scavenger in the blend of blowing
agents, the acid scavenger provides for costabilization. The results shown
in FIGS. 4 and 10 illustrate this point. The costabilizer can be metal
salts of phosphoric acids, or other acid acceptors that are not
detrimental to the base CPVC resin used. Specific examples of metals salts
of phosphoric acid include water-soluble, alkali metal phosphate salts,
disodium hydrogen phosphate, orthophosphates such as mono-, di-, and
triorthophosphates of said alkali metals, alkali metal phosphates and the
like. Examples of acid acceptors not detrimental to the base CPVC resin
include aluminum magnesium hydroxy carbonate hydrate, magnesium aluminum
silicates and alkali metal alumino silicates. An example of a commercially
available aluminum magnesium hydroxy carbonate hydrate is Hysafe 510,
available from the J. M. Huber Company. Examples of magnesium aluminum
silicates are molecular sieves such as for example Molsiv Adsorbent Type
4A from UOP. Examples of alkali metal alumino silicates are zeolites such
as CBV 10 A Zeolite Na-Mordenite by Synthetic Products Co. The most
preferred costabilizer is disodium hydrogen phosphate (DSP). The DSP can
be added separately to the foamable composition or can be added to the
CPVC polymer during the processing of the CPVC polymer. Usually from about
0.1 to about 3 parts by weight of the costabilizer are added to the
composition per 100 parts by weight of chlorinated polyvinyl chloride
polymer, if added at all. In the preferred embodiment, 1.3 parts by weight
of disodium hydrogen phosphate is added to 100 parts of the CPVC polymer.
The costabilizer is superior to merely increasing the tin stabilizer level
since increasing the amount of tin stabilizer lowers the heat deflection
temperature of the foam and is undesirable in typical end use
applications.
The medium density foamed composition of the instant invention also
optionally contains an impact modifier. Examples of impact modifiers
include acrylic impact modifiers, methacrylate-butadiene-styrene (MBS)
impact modifiers, silicone rubber/acrylic copolymers impact modifiers,
acrylonitrile-butadiene-styrene (ABS) impact modifiers and chlorinated
polyethylene (CPE) impact modifiers. Generally when used, less than 10
parts of the impact modifier is added to the foamed CPVC composition. The
preferred impact modifiers include acrylic impact modifiers, MBS impact
modifiers, silicone rubber/acrylic copolymer and ABS impact modifiers,
listed in descending order of preference, the most preferred impact
modifiers are acrylic impact modifiers.
U.S. Pat. No. 3,678,133 describes the compositions conventionally referred
to as acrylic impact modifiers. Generally, as stated in column 2, the
impact modifier is a composite interpolymer comprising a multi-phase
acrylic base material comprising a first elastomeric phase polymerized
from a monomer mix comprising at least 50 wt. % of an alkyl acrylate
having about 2-8 carbon atoms in the alkyl group and a minor amount of a
crosslinking agent and a second rigid thermoplastic phase polymerized from
a monomer mix comprising at least 50% alkyl methacrylate having 1-4 carbon
atoms in the alkyl group and having a molecular weight of from 50,000 to
600,000. (Lines 10-20). Further, the patent states that the polymerization
of the rigid thermoplastic phase is preferably conducted in such a fashion
that substantially all of the rigid phase material is formed on or near
the surface of the elastomeric phase. (Lines 34-39). Acrylic impact
modifiers are polyacrylates including (C.sub.4 -C.sub.12) acrylate homo or
copolymers, second stage graft polymerized with methyl methacrylate,
polybutyl acrylate jointly graft copolymerized with methyl methacrylate
and styrene, poly(ethylhexyl acrylate-co-butyl acrylate) graft
copolymerized with styrene, and/or acrylonitrile and/or
methylmethacrylate; polybutyl acrylate graft polymerized with
acrylonitrile and styrene (Blendex 975, 977 or 979 (Blendex is a trademark
of GE Plastics)). Other commercial embodiments are available from Rohm &
Haas under the trademarks Paraloid KM 334, KM 365 and KM 330. The most
preferred acrylic impact modifier is Paraloid KM 330 impact modifier. If
used as an impact modifier in the composition, 10 parts of the Paraloid KM
330 acrylic impact modifier are added.
MBS impact modifiers are graft polymers. Generally MBS impact modifiers are
prepared by polymerizing methyl methacrylate or mixtures of methyl
methacrylate with other monomers in the presence of polybutadiene or
polybutadiene-styrene rubbers. When added to the foamed CPVC composition,
about 5 to about 15 parts of MBS impact modifiers are used. Preferably, 5
to about 10 parts of MBS impact modifier are used. Most preferably, 6
parts are used. Examples of commercially available MBS impact modifiers
include Kane Ace B-56 and Kane Ace B-22, available from Kaneka; and
Paraloid KM 680, available from Rohm & Hass. The most preferred impact
modifier is Kane Ace B-56.
Polyorganosiloxane impact modifiers can also be used. The most preferred
impact modifier is composed of a mixture of a polyorganosiloxane and a
polyalkyl (meth)acrylate. Preferably, the impact modifier contains about
10-90% by weight of the polyorganosiloxane and from about 10 to 90% by
weight of a polyalkyl (meth)acrylate.
The polyorganosiloxane may be prepared by emulsion polymerization using an
organosiloxane and a crosslinking agent as described hereinafter. At that
time, a grafting agent may further be used.
The organosiloxane may be various types of cyclic siloxanes of at least
three-membered ring, preferably from 3- to 6-membered cyclosiloxanes. For
example, it is believed hexamethylcyclotrisiloxane,
octamethylcyclotetrasiloxane, decamethylcyclo-pentasiloxane,
dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane,
tetramethyltetraphenylcyclotetrasiloxane and octaphenylcyclotetrasiloxane
can be used. These organosiloxanes may be used alone or in combination as
a mixture of two or more different types. The organosiloxane is used in an
amount of at least 50% by weight, preferably at least 70% by weight of the
polyorganosiloxane.
The crosslinking agent for the organosiloxane may be a trifunctional or
tetrafunctional silane type crosslinking agent such as
trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane,
tetraethoxysilane, tetra-n-propoxysilane or tetrabutoxysilane.
Tetrafunctional crosslinking agents are particularly preferred, and among
them tetraethoxysilane is especially preferred. The crosslinking agent is
used usually in an amount of from 0.1 to 30% by weight in the
polyorganosiloxane.
The grafting agent for the organosiloxane may be a compound capable of
forming a unit represented by the formula:
##STR1##
wherein R.sup.1 is a methyl group, an ethyl group, a propyl group or a
phenyl group. R.sup.2 is a hydrogen atom or a methyl group, n is 0, 1 or
2, and p is a number o from 1 to 6.
The polyorganosiloxane can be prepared by any method in which the
organosiloxane, the crosslinking agent and optionally the grafting agent
are mixed. The preparation is well within the scope of one of ordinary
skill in the art, and does not form part of this invention.
The polyorganosiloxane can be compounded with (meth)acryloyloxysiloxane
capable of forming the unit of the formula (I-1). A methacryloyloxysilane
is particularly preferred as the compound capable of forming the unit of
the formula (I-1). Specific examples of the methacryloyloxysilane include
.beta.-methacryloyloxyethyldimethoxymethylsilane,
.tau.-methacryloyloxypropylmethoxydimethylsilane,
.tau.-methacryloyloxypropyldimethoxymethylsilane,
.tau.-methacryloyloxypropyltrimethoxysilane,
.tau.-methacryloyloxypropylethoxydiethylsilane,
.tau.-methacryloyloxypropyldiethoxymethylsilane and
.delta.-methacryloyloxybutyldiethoxymethylsilane. The grafting agent is
used usually in an amount of from 0 to 10% by weight in the
polyorganosiloxane.
The polyalkyl (meth)acrylate may be prepared using an alkyl (meth)acrylate,
a crosslinking agent and a grafting agent. The alkyl (meth)acrylate may be
an acryl acrylate such as methyl acrylate, ethyl acrylate, n-propyl
acrylate, n-butyl acrylate or 2-ethylhexyl acrylate, or an alkyl
methacrylate such as hexyl methacrylate, 2-ethylhexyl methacrylate or
n-lauryl methacrylate. It is particularly preferred to use n-butyl
acrylate. The crosslinking agent for the alkyl (meth)acrylate may be, for
example, ethylene glycol dimethacrylate, propylene glycol dimethacrylate,
1,3-butylene glycol dimethacrylate or 1,4-butylene glycol dimethacrylate.
The grafting agent for the alkyl (meth)acrylate may be, for example, allyl
methacrylate, triallyl cyanurate or triallyl isocyanurate. Allyl
methacrylate can be used alone as a crosslinking agent. The preparation of
the polyalkyl (meth)acrylate is well within the scope of one of ordinary
skill in the art and does not form part of this invention.
The two components, the polyorganosiloxane and the polyalkyl
(meth)acrylate, can be polymerized together to form the impact modifier in
a manner such as for example described by European Patent EP 0308871 A2,
incorporated herein by reference. Any other method may be used to combine
the two components, including those known within the art. The
polymerization of the two components is well within the scope of one of
ordinary skill in the art and does not form part of this invention.
The preferred impact modifier contains polydimethyl siloxane. Most
preferably, the impact modifier comprises a butyl acrylate-methyl
methacrylate-poly(dimethyl siloxane) copolymer. An example of a
commercially available polyorganosiloxane impact modifier is
Metablen-S-2001 manufactured by the Mitsubishi Rayon Co. and available
from Metco North America. Desirably, from about 2 parts to about 15 parts
of the impact modifier containing polyorganosiloxane are added to the
composition to be foamed. Preferably, 6 parts of the impact modifier
containing a polyorganosiloxane are added to the composition.
Similarly, ABS impact modifiers can be used in the foamed CPVC composition.
ABS modifiers are usually prepared by polymerizing styrene and
acrylonitrile in the presence of polybutadiene rubber. Examples of
commercially available ABS impact modifiers which can be used in the
instant invention include Blendex 338, Blendex 310 and Blendex 311; all
available from GE Plastics. If used as the impact modifier of choice,
approximately 5 parts to about 15 parts of ABS impact modifier are used.
Preferably, 6 parts of the ABS impact modifier are used.
Chlorinated polyethylene (CPE) impact modifiers can also be used. Generally
these CPE impact modifiers are lower molecular weight impact modifiers.
Generally, these CPE impact modifiers should have a weight average
molecular weight in the range of about 70,000 to about 96,000; and a
number average molecular weight in the range of 18,000 to about 24,000.
These CPE impact modifiers are prepared by chlorinating high-density
polyethylene. These chlorinated polyethylene have a specific gravity of
from about 1.13 to 1,4, preferably 1.16 and a residual crystallinity of
from about 0 to 25%, preferably 0 to 10% and a chlorine content from about
25% to about 45%, preferably 35 to 44%. The chlorination can be either
homogeneous or heterogeneous, preferably to a small extent. Chlorination
methods for CPE include aqueous suspension, solution or gas phase methods.
The preferred method is by suspension chlorination. CPE is commercially
available from DuPont Dow under the tradename Tyrin 3611P CPE, Tyrin 3615P
CPE, and Tyrin 4211P CPE. Similarly, another example of a commercial CPE
is Elaslen 303BS CPE, available from Showa Denko. The amount of CPE
present ranges from about 0.1 to about 20, if CPE is used as the impact
modifier. The preferred CPEs include DuPont Dow Tyrin 421 IP CPE and Tyrin
361 1P CPE. The most preferred CPE is Tyrin 4211P CPE. Preferably, 6 parts
of the CPE impact modifier are used, if used at all.
A high molecular weight process aid is optionally included in the foamable
composition. The high molecular weight process aids are necessary to
provide melt elasticity or melt strength of the polymer melt formed within
the extruder and high integrity of the foam cell walls during extrusion.
High molecular weight process aids can be either acrylic process aids or
copolymers of styrene and acrylonitrile. Suitable high molecular weight
process aids include those high molecular process aids known in the art.
The acrylic process aids which can be used in the instant invention are
thermoplastic polymethyl methacrylate homo or copolymers with weight
average molecular weights greater than 1,000,000. Hard, glassy copolymers
of styrene and acrylonitrile having a glass transition temperature in
excess of 60.degree. C. and a dilute solution viscosity greater than 1.5
as measured in methylethyl ketone at 4% concentration and is selected from
copolymers if styrene and an unsaturated nitrile containing more than 50%
of said styrene and 10 to 40% of said nitrile are examples of the styrene
acrylonitrile process aids. Examples of styrene-acrylonitrile polymers
suitable for use in the foamable composition are Goodrite 2301.times.36,
manufactured by the Zeon Company and Blendex 869 from General Electric
Plastics. If added at all, 10 parts of the styrene acrylonitrile copolymer
are added to the composition per 100 parts of CPVC polymer. Generally, the
higher the weight average molecular weight of the acrylic process aids,
and the less acrylic processing aid should be added. Examples of suitable
acrylic process aids include poly(methyl methacrylate) available under the
trade name Paraloid K-400, Paraloid K-128N, Paraloid K-125, all from Rohm
& Haas; and the trade name Kaneka PA 10, Kaneka PA 20 and Kaneka PA 30,
all three from Kaneka Tex. Another suitable acrylic process aid includes
2-propenoic acid, 2-methyl ester polymer with butyl 2-propinoate. This
acrylic process aid is commercially available as Metablen P530 from Elf
Atochem. If Metablen P530 is used as the acrylic process aid, generally
about 2 parts are used. Generally, from about 2 to about 20 parts of the
acrylic process aid are added per 100 parts of CPVC. Preferably, from
about 6 to about 10 parts of the acrylic process aid are added per 100
parts of CPVC. Most preferably, 6 parts of an acrylic process aid per 100
parts of CPVC are used, if used at all.
The foamable composition preferably includes lubricants or lubricant
mixtures. This includes any lubricants known to those in the art. Suitable
lubricants include for example but not limited to various hydrocarbons
such as paraffin; paraffin oils; low molecular weight polyethylene;
oxidized polyethylene; amide waxes, metal salts of fatty acids; esters of
fatty acids such as butyl stearate; fatty alcohols, such as cetyl, stearyl
or octadecyl alcohol; metal soaps such as calcium or zinc salts of oleic
acid; fatty amides of organic acids; polyol esters such ad glycerol
monostearate, hexaglycerol distearate and mixtures thereof. Examples of
possible fatty acids to be used include but are not limited to stearic
acid and calcium stearate. Examples of fatty amides of organic acids
include stearamide, and ethylene-bis-stearamide. Since several lubricants
can be combined in countless variations, the total amount of lubricant can
vary from application to application. Optimization of the particular
lubricant composition is not within the scope of the present invention and
can be determined easily by one of ordinary skill in the art. Generally
from about one to about ten parts of lubricant are added to the foamable
composition per one hundred parts of CPVC polymer. Preferably the
following mixture of lubricants is used: Glycolube 674, an ester of a
fatty acid (available from the Lonza Co.); Loxiol G-70, a proprietary
fatty acid ester, (available from Henkel) and Aristowax 145, a paraffin
wax (available from Unocal). In the preferred embodiment, the lubricant
package includes 1.5 parts by weight of oxidized polyethylene, 0.5 parts
of the proprietary fatty acid ester and 0.5 parts of a fatty acid (based
upon 100 parts of CPVC polymer) are added to the foamable composition.
The foamable composition may also possibly include a metal release agent if
desired, but not necessary. Metal release agents are materials which are
incompatible with the polymer melt and lubricate the melt against the
surface in which the material is being processed. An example of a metal
release agent is a terpolymer of methylmethacrylate, styrene and butyl
acrylate. The terpolymer of methylmethacrylate, styrene and butyl acrylate
is available under the trade name of Paraloid K-175, available from Rohm &
Haas. Preferably 1.0 parts of this terpolymer per 100 parts of CPVC
polymer are added to the lubricant.
The foamable composition may also optionally include an activator.
Generally, such an activator is used when a lower temperature for the
foamable composition is desired in the extruder as well as when complete
decomposition of the nitrogen containing blowing agent is desired. The
activator helps the portion of the nitrogen containing decomposition type
blowing agent to decompose faster and to generate more gases than when not
used. Examples of suitable activators include tin salts of monocarboxylic
acids and organo tin stabilizers. Examples of such organo-tin stabilizers
include without limitation: dibutyltin dilaurate, dibutyltin maleate,
di(n-octyl) tin maleate, dibutyltin bis(lauryl mercaptide), dibutyltin,
S,S-bis(isooctyl thioglycoate), dibutyltin .beta.-mercaptoproprionate,
di-n-octyltin S,S-bis(isooctyl thioglycolate), and di-n-octyltin
.beta.-mercaptoproprionate. The most preferred activator is dibutyl tin
dilaurate. The activator may be included in any amount useful to cause the
activation. An example of an activator is Thermolite 149 from the Elf
Atochem Company. Generally, 0.5 parts of activator may be included per 100
parts of CPVC polymer. However, use of such activator may reduce the heat
distortion temperature of the final foam.
In addition, enhancing ingredients useful to enhance either the processing
of a CPVC or the CPVC foam product can be included in the foamable
composition. These include for example but not limited to pigments, such
as titanium dioxide, carbon black, and iron oxide, fillers such as calcium
carbonate, silica and the like, reinforcing agents such as glass fibers,
and graphite fibers or glass spheres, other processing aids, impact
modifiers, and alloying agent and the like, antioxidants, and antistatics.
An example of an alloying agent is chlorinated polyethylene. Any
chlorinated polyethylene can be used as the alloying agent. If an alloying
polymer is used, preferably 0 to 5 parts of the alloying polymer are added
per 100 parts of CPVC resin. Preferably, 3 parts of chlorinated
polyethylene per 100 parts of CPVC polymer are included in the
composition. An example of a suitable chlorinated polyethylene to be used
in the instant invention includes Tyrin 3611P CPE and Tyrin 4211P CPE from
the DuPont Dow Chemical Company. These enhancing ingredients can be added
in an amount effective for the intended purpose. The amount and use of the
alloying agent would be within the purview of one of ordinary skill in the
art and does not form part of this invention.
The ingredients for the foamable composition can be combined in any
convenient manner and formed into a foam by the free blown or Celuka
process or any process known in the art to foam. The method chosen to foam
the material is within the skill of one of ordinary skill in the art. For
example, all the ingredients can be mixed together uniformly by mixing
means such as a Henschel high intensity mixer or other mixing means and
then added to an extruder equipped with heating elements. Any extruder
useful for processing of CPVC polymer can be used to foam the foamable
composition provided the die is appropriately chosen. Preferably, a short
land length is desired in the extruder die. Examples of suitable extruders
include the Cincinnati Milacron CM-55 counter-rotating conical screw
extruder and the Davis Standard 2.5 inch single screw extruder. The amount
of the blowing agent, the extruder temperature and the screw speed of the
extruder can be varied to obtain the desired specific gravity of the
foamed product is well within the skill of one of ordinary skill in the
art.
As the foam composition goes through the extruder, it is heated and
converted into a viscous melt. The chemical blowing agent is also
activated and begins to decompose when the melt reaches a temperature of
approximately 120.degree. Centigrade to approximately 200.degree.
Centigrade. However, although the gases are formed due to the
decomposition of the blowing agent, the foamable composition does not
expand while in the extruder. When the hot foam composition is discharged
from the extruder through the extruder head into the atmosphere which has
reduced pressure, the blowing agent expands the foam composition into the
desired cellular product.
Alternatively, a two pellet system can be used in the free blown process.
In this system, the CPVC polymer, tin stabilizer, impact modifier (if
used), the costabilizer (if used), high molecular weight process aid (if
used) and lubricant package can be mixed in an extruder. The extrudate can
be cubed or otherwise pelletized to form the first pellet and stored for
latter processing. In addition to the chemical blowing agent, other
optional enhancing ingredients as well as a polymer alloying agent such as
chlorinated polyethylene can be mixed together in an extruder at a
temperature below the decomposition temperature of the chemical blowing
agent to form the second pellet. In the preferred embodiment, 2.1 parts of
chlorinated polyethylene are added to the chemical blowing agent to form
the second pellet. Preferably, either Tyrin 3611P CPE or 4211P CPE are
used. Most preferably, Tyrin 4211P CPE is used. The extrudate can be cubed
or otherwise pelletized and stored for processing as the second pellet.
The first and second pellets are the same size to promote uniform
blending. When desired, the first and second pellets or cubes can be mixed
together and extruded. As described above, the composition expands into a
foam when the extrudate reaches the atmosphere.
The preferred method of mixing the ingredients of the foamable composition
is the two pellet method. First, this method gives the flexibility to
decide the amount of blowing agent to be added to the composition and
thereby customizing the density of the foamed CPVC. Second, due to the
difficulty in processing CPVC directly from powder, it is beneficial that
a high work input melt fusion can be used in forming the first set of
pellets, otherwise one may encounter inconsistent foaming. Further, the
first pellet can be dried in a desiccant dryer to remove moisture which is
often undesirable since moisture is a physical blowing agent and if
uncontrolled, may result in uncontrollable foaming.
There are many uses of the medium density foam composition. For example,
the composition can be used in woodlike fenestration components, such as
for example but not limited to, window and door components. In addition,
the foam can be used for construction, electrical and fluid handling
applications such as roofing, siding, fencing, electrical junction boxes,
plenum materials, track lighting, electrical enclosures, automotive;
aircraft and mass transit interiors; drain, waste, and vent pipes; and
other low pressure pipes.
The following non-limiting examples serve to further illustrate the present
invention in greater detail.
EXAMPLES
In the Examples, the two pellet method is generally used. "CBA" refers to
the chemical blowing agent.
TABLE 1
__________________________________________________________________________
SERIES 1,"
EXP. A
EXP. B
EXP. C
EXP. D
parts
parts
parts
parts
__________________________________________________________________________
TempRite 677x670, CPVC Resin, Suspension Grade, 0.68
100.0
100.0
100.0
100.0
IV, 67% Cl, without DSP formed from Geon 110x440 PVC
from The Geon Co.
Mark 2925, Tin Stabilizer from Witco
3.5 3.50
3.50
3.5
Goodrite 2301x36, Acrylic Processing Aid
4.0 4.00
4.00
4.0
Zeon Company
Metablen S-2001, Silicone/Acrylic Impact Modifier, Meteo
6.0
North America
Kane Ace B-56, MBS Impact Modifier, Kaneka
6.00
Tyrin 2000 CPE, DuPont Dow Co. 6.00
Paraloid KM334, Acrylic Impact Modifier, DuPont Dow
10.0
AC629-A, Oxidized Polyethylene, Allied Signal
1.5 1.50
1.50
1.5
G-70 Beads, Fatty Acid Ester Wax, Henkel Loxiol
1.0 1.00
1.00
1.0
Microthene FN 510, Low Molecular Weight Polyethylene,
0.5 0.50
0.50
0.5
Quantum Chemical Corp.
Irganox 1010, Antioxidant, Ciba-Geigy Corp.
0.25
0.25
Tioxide R-FC 6, Tioxide America, Inc.
3.0 3.00
3.00
3.0
__________________________________________________________________________
______________________________________
SERIES 1, TABLE 2
______________________________________
CBA Pellet 1
69% Dow Tyrin 4211 P
CPE (CBA carrier agent)
31% Unicell D-200
Azodicarbonamide CBA
CBA Pellet 2
69% Dow Tyrin 4211P
CPE (CBA carrier agent)
31% Exocerol 232
Commercial Bicarbonate/Azodicarbonamide
CBA blend
CBA Pellet 3
81.5% Dow 4211P
CPE (CBA carrier agent)
15.5% Exocerol 232
Bicarbonate/Azodicarbonamide CBA blend
3% Pigment Red Pigment, Harshaw Citation B-1051,
Engelhard Corp.
CBA Pellet 4
81.5% Dow Tyrin 3615P
CPE (CBA carrier agent)
15.5% Exocerol 232
Bicarbonate/Azodicarbonamide CBA blend
3% Pigment Blue Pigment, Irgalite Blue BCS, Ciba Geigy
Corp.
______________________________________
The following tests were performed on the mixtures of Pellet A and B as set
forth in Table 3:
______________________________________
Dynamic Thermal Stability Test
Described Below
Izod Impact Test, Notched at 72.degree. F.
ASTM D-256
Tensile Strength Test at 72.degree. F.
ASTM D-638
Flexural Strength Test at 72.degree. F.
ASTM D-790
Coefficient of Thermal Expansion (CTE),
ASTM D-696
-30 to +30C, .times. 10.sup.-5 in/in C
Specific Gravity ASTM D-792
______________________________________
The Dynamic Thermal Stability Test (DTS Test) is a procedure developed by
The B. F. Goodrich Company to determine the dynamic thermal stability
(DTS) of CPVC compounds. DTS is defined as the time required to raise the
machine torque on a Brabender Electronic Plasticorder, Model EPL-VS501
(Type 6, 60/83 MC, 3:2 drive ratio, Type SB Roller Type Rotors, Stainless
Steel 376) by 100 metergrams from the lowest torque attached by the
polymer set at a given temperature and mixing rotor speed. Connected to
the Brabender Electronic Plasticorder drive unit is an electrically heated
Haake Rheomix fusion head.
In all the DTS Tests run in this patent application, 70 grams of
sample/1.50 specific gravity were used, mixing bowl temperature of
194.degree. C., loading time 2 minutes, loading and preheat time of 3.0
minutes. The rotor speed was 35 rpm. The Brabender Electronic Plasticorder
is operated in accordance with the instructions set forth in the operating
manual. The torque is recorded. These tests show the degradation effects
of the CBA on CPVC resins.
TABLE 3
__________________________________________________________________________
SERIES 1 OF EXPERIMENTS-RESULTS
Pellet A EXP A EXP B EXP C EXP D
__________________________________________________________________________
w/o CBA
Time, min. 15.3 12.4 15.3 15.2
Torque, mg. 2190 2300 2000 2180
Temperature, .degree.C.
209 211 208 210
DTS: w/3% CBA Pellet 1
Time, min. 8.8 6.0 7.4 7.2
Torque, mg. 2200 2300 2080 2200
Temperature, .degree.C.
209 209 208 210
DTS: w/1.25% CBA Pellet 2
Time, min. 16.1 14.2 16.7 16.6
Torque, mg. 2230 2360 2090 2200
Temperature, .degree.C.
211 209 208 209
Izod Impact, w/o CBA, in.-lb./in.
1.7C 8.9P 5.5C
Tensile Strength, w/o CBA @ Yield, psi.
7120 7270 6790
w/o CBA @ Break 6430 5880 6060
Modulus, w/o CBA, psi.
373,000
397,000 343,000
% Elongation 30 25 53
Flexural Strength, w/o CBA, psi.
13,623
13,910 12,859
Modulus, w/o CBA, psi.
395,713
403,775 370,441
CTB, w/o CBA .times. 10.sup.-5 in/inC
7.13 6.92 7.78
Specific Gravity, w/o CBA, g/cc
1.49 1.48 1.47
__________________________________________________________________________
The results of Table 3, Series 1 Experiments are set forth in a bar graph
in FIG. 1.
The following conclusions can be drawn from this series of experiments.
First, the blend of the bicarbonate/azodicarbonamide blowing agent
improves the thermal stability of the compound which can be foamed as
compared to the azodicarbonamide itself. Second, adding azodicarbonamide
blowing agent itself results in degradation of the CPVC compound used to
form the medium density foam. Third, the bicarbonate blowing agent in the
blend acts as a costabilizer in the CPVC compound.
The effect of the various impact modifiers on the CPVC foam compounds were
studied as set forth in Table 4. In this table, the letters "C" and "P"
characterize the type of break that occurs. "C" means complete break,
where "P" means partial break in the Notched Izod Impact Test.
Table 5 sets forth the properties of the compositions in Table 4 combined
with a blowing agent. In this table, a VHIT value designated as "D"
indicates it was ductile, whereas "T" indicates it was transitional.
TABLE 4
__________________________________________________________________________
Pellet A EXP A
EXP B
EXP C
EXP D
__________________________________________________________________________
TempRite 677x670, CPVC, 68 I.V., 67% CL
X X X X
Process Aid X X X X
Silicone/Acrylic Impact Modifier
X
MBS Impact Modifier X
CPE Impact Modifier X
Acrylic Impact Modifier X
DTS,
w/o CBA Time, min. 15.3 12.4 15.3 15.2
w/3% CBA Pellet 1 Time, min.
8.8 6.0 7.4 7.2
w/1.25% CBA Pellet 2 Time, min.
16.1 14.2 16.7 16.6
Izod Impact, w/o CBA, in.-lb./in.
1.7C 8.9P 5.5C
CTE, w/o CBA .times. 10.sup.-5 in/in C
7.13 6.92 7.78
__________________________________________________________________________
TABLE 5
__________________________________________________________________________
EXP. A EXP. A EXP. B EXP. D EXP. D EXP. D
with 31% with 31%
with 31% with 15.5%
with 31% with 31%
Pellet A/Pellet B
Azodicarbonamide
Exocerol 232
Azodicarbonamide
Exocerol 232
Azodicarbonamide
Exocerol
__________________________________________________________________________
232
% CBA Pellet B used:
3.00 1.25 3.00 2.50 3.00 1.25
Approximate Density
0.92 0.70 0.81 0.68 0.89 0.76
Lab Spec. Grav.
0.89 0.77 0.80 0.83 0.92 0.69
Izod Impact 0.38/C 0.51/C 0.75/C 0.91/C 0.41/C 1.25/C
Vhit, 3/8", in.lb/mil. X
0.33/D 0.33/D 0.32/D 0.22/D 0.33/D 0.33/D
Tensile
@ Yield 2,780.00 2,320.00
2,320.00 2,910.00
3,190.00 1,930.00
@ Break 2,900.00 2,380.00
2,460.00 2,870.00
3,290.00 2,000.00
Modulus 149,000.00
120,000.00
126,000.00
160,000.00
173,000.00
107,000.00
% Elongation
34.00 23.00 36.00 23.00 38.00 23.00
Flexural Strength
6,020.00 4,886.00
4,884,00 5,780.00
7,375.00 4,262.00
Modulus 165,543.00
141,021.00
130,729.00
164,187.00
200,670.00
122,106.00
__________________________________________________________________________
The results in this Table indicate that the use of a higher molecular
weight chlorinated polyethylene as a carrier agent in Pellet B does not
change the foam density, processability or the foam properties developed.
The following series of experiments, set forth in Tables 6 and 7, were
carried out on a 21/2 inch Davis Standard Extruder having the following
profile extrusion metering screw configuration:
______________________________________
Screw 21/2 in. 60 mm diameter
L/D 24:1
Feed 5 @ 0.400", 5 flights
Transition , 7 flights
Metering 12 @ 0.200" exit depth, 12 flight
______________________________________
In addition, there are 4 rows of interruption mixing pins set forth in the
metering region of the screw. These mixing pins are arbitrarily placed in
the metering region to interrupt the flow.
TABLE 6
______________________________________
EXP. A EXP. B EXP. C
EXP. D
Pellet A/*CBA Pellet
CBA CBA CBA CBA
2 Pellet B Pellet 2
Pellet 4 Pellet 2
Pellet 3
______________________________________
Barrel:
zone #1, .degree.F.
340 340 340 340
zone #2, .degree.F.
350 350 350 350
zone #3, .degree.F.
360 360 360 360
zone #4, .degree.F.
360 360 360 360
Die #1, .degree.F.
360 360 360 360
Screw, rpm 20 20 20 20
Amps 13 13 11 13
Head Press, psi
1760 1840 1780 1900
Stock Temp, .degree.F.
398 396F
Rate, lbs/hr 100 103
Rough density
0.70 0.68 0.76
______________________________________
TABLE 7
______________________________________
EXP. A/ EXP. B/ EXP. C/
EXP. D/
Pellet A/ 3% CBA 13% CBA 3% CBA 3% CBA
CBA Pellet B
Pellet 1 Pellet 1 Pellet 1
Pellet 1
______________________________________
Barrel:
zone #1, .degree.F.
350 345 345 345
zone #2, .degree.F.
360 355 355 355
zone #3, .degree.F.
370 365 365 365
zone #4, .degree.F.
370 365 365 365
Die #1, .degree.F.
370 365 365 365
Screw, rpm 25 25 25 25
Amps 12.5 13 11 13
Head Press, psi
1760 1620 1670 1870
Rate, lbs/hr
121 114 118 116
Rough density
0.92 0.81 n.a. 0.89
______________________________________
Note: All Pellet "A" blended w/3% CBA Pellet 1
In the next series of experiments, the following compositions for Pellets A
and Pellet B, set forth in Tables 8 and 9 were used:
TABLE 8
__________________________________________________________________________
SERIES 2 OF EXPERIMENTS
EXP. E
EXP. F
EXP. G
EXP. H
EXP. I
EXP. J
Pellet A parts
parts
parts
parts
parts
parts
__________________________________________________________________________
TempRite 673x670,
75 75 75 75 75 75
Suspension Grade 0.68 IV,
67.0% Cl with DSP, (Base
PVC: Geon 110x440)
TempRite 639x683,
25 25 25 25 25 25
Suspension Grade 0.51 IV,
68.5% Cl with DSP, (Base
PVC: Vista 5225)
Mark 292S, Tin Stabilizer,
3 3 3 3 3 3
Witco Corp.
Metablen P530, from Elf
2 4
Atochem
Goodrite 2301x36, Acrylic
4 6 6
Processing Aid, Zeon
Chemical
Paraloid KM 330, Acrylic
10 10 10 10
Impact Modifier, DuPont
Dow
Kane Ace B-56, MBS 6
Impact Modifier, Kaneka
Blendex 338, ABS Impact 6
Modifier, GE Plastics
AC 629A, Oxidized
1.5 1.5 1.5 1.5 1.5 1.5
Polyethylene, Allied
Signal
G-70 Beads, Fatty Acid
1.0 1.0 1.0 1.0 1.0 1.0
Ester Wax from Henkel
Loxiol
Microthene FN-510, Low
0.5 0.5 0.5 0.5 0.5 0.5
Molecular Weight
Polyethylene
Tioxide R-FC 6, Titanium
3 3 3 3 3 3
dioxide, Tioxide America, Inc.
__________________________________________________________________________
TABLE 9
______________________________________
Pellet "B's"
CBA Pellet 5
67% Dow 4211P CPE (CBA carrier agent)
31% Unicell D-200
Azodicarbonamide CBA
2% Pigment Yellow Pigment - (Irgazine 3-RLT-N,
available from Ciba Geigy)
CBA Pellet 6
82.5% Dow Tyrin 4211P
CPE (CBA carrier agent)
15.5% Exocerol 232
Commercial Bicarbonate/Azo-
dicarbonamide CBA blend
0.2% Pigment Yellow Pigment
1.8% Pigment Blue Pigment (Irgalite Blue BCS,
available from Ciba Geigy)
CBA Pellet 7
82.5% DuPont Dow Tyrin 4211P
CPE (CBA carrier agent)
15.5% Hydrocerol BIF
Bicarbonate CBA
2.0% Pigment Blue Pigment (Irgalite Blue BCS,
available from Ciba Geigy)
______________________________________
The effect of CBA blend ratios on Experiment E, Pellet A, was studied below
in Table 10. The following results were obtained for the DTS Test
described in further detail and carried out at 194.degree. C. bowl
temperature, with a rotor blade speed at 35 RPM. The pellets (70 grams)
are introduced into the DTS head with a 3 min. load/soak, before the test
is obtained. The purpose of these experiments was to attempt to determine
the optional blend of an azodicarbonamidelbicarbonate CBA required to
extrude a medium density CPVC foamed profile with good processability.
TABLE 10
__________________________________________________________________________
10-0
10-1
10-2
10-3
10-4
10-5
10-6
__________________________________________________________________________
Pellet A, Exp. E
100 100 100 100 100 100 100
3.5% CBA Pellet 5
1.09
0.88
0.65
0.43
0.22
--
(31% azodicarbonamide)
1.99% CBA Pellet 7
0 0.06
0.12
0.18
0.24
0.3
(15% bicarbonate)
DTS Test
Time, min. 26.5
7.2 9.6 13.5
16.5
19.7
31
Torque, mg 2200
2200
2260
2210
2210
2210
22
Temperature, .degree.C.
211 209 210 211 211 211 21
Plate-Out LT. Med.
LT. LT. LT. LT. --
Med.
__________________________________________________________________________
Plate-Out in Table 10 refers anything incompatible with the polymer, and
coats the interior of metal surfaces.
The conclusions that can be drawn from this series of experiments includes
the following. First, displacing the azodicarbonamide CBA with bicarbonate
CBA does not mean that the cells in the foam will become coarser in a
linear fashion. The addition of the azodicarbonamide tends to nucleate the
microvoid (since the nitrogen cannot diffuse easily through the CPVC) into
a well dispersed manner and the bicarbonate CBA's CO.sub.2 gas expands the
void but the cell diameter remains much smaller than if the bicarbonate
was used alone. The DTS tests clearly show the advantage of using as much
bicarbonate CBA in a blend as the processing will allow.
Table 10 are shown in Bar Graph form in FIG. 2. SBC in this Figure refers
to sodium bicarbonate.
The tests set forth in Table 11 were carried out on the 21/2 Davis Standard
Extruder, set according to the same configuration as set forth for Tables
6 and 7 above.
TABLE 11
__________________________________________________________________________
EXP. E EXP. E EXP. E EXP. E
EXP. E Blend 1 Blend 2 Blend 3 Blend 4
Pellet A
3.5% CBA 5
2.8% CBA Pellet 5
2.1% CBA Pellet 5
1.4% CBA Pellet 5
0.7% CBA Pellet
EXP. E
Pellet B
Pellet 5
0.38% CBA Pellet 7
0.77% CBA Pellet 7
1.16% CBA Pellet 7
1.55% CBA Pellet
1.94% CBA Pellet
__________________________________________________________________________
7
Barrel:
zone #1, .degree.F.
340 340 340 340 340 340
zone #2, .degree.F.
355 355 355 355 355 355
zone #3, .degree.F.
365 365 365 365 365 365
zone #4, .degree.F.
365 365 365 365 365 365
Die #1, .degree.F.
365 365 365 365 365 365
Screw, rpm
20 20 20 20 20 20
Amps 13 12 12 12 12 12
Head Press, psi
1495 1470 1520 1490 1495 1500
Rate, lbs/hr 98 102 99
Rough density
0.86 0.81 0.79 0.75 0.75 0.89
Comments:
Good Control;
Good Control; More
Good Control;
Slightly Less Control;
Same as Blend
Unsizable; Chatter
in
Low Center
Center Flow;
Easy to Size
Center Void; Slight
Broke 2x, pulsation
sizer; Pulsation
Flow; Easy to
Easy to Size Pulsation
Size
__________________________________________________________________________
The bar graph in FIG. 3 illustrates the DTS results of the experiments set
forth in Table 12. From these results, one can conclude that even without
the conventional costabilizer, pages 9-10 added to the CPVC, the blend of
a bicarbonate/azodicarbonamide CBA provides improved processability over
the use of just an azodicarbonamide CBA or a bicarbonate CBA. This affirms
the conclusion that the bicarbonate functions as a costabilizer for the
CPVC compound itself.
The effect of CBA blend ratios on DTS was also studied in conjunction with
Pellet A, Exp. D. The same conditions for DTS as used in Table 10 are used
in this Table 12.
TABLE 12
______________________________________
12-1 12-2 12-3 12-4 12-5 12-6
______________________________________
Pellet A, Exp. D
100 100 100 100 100 100
Pellet B,
3.5% CBA Pellet 5
1.09 0.88 0.65 0.43 0.22 --
(% azodicarbon-
amide)
1.94% CBA Pellet 7
-- 0.06 0.12 0.18 0.24 0.30
(% bicarbonate)
Test, DTS
Time (min.)
5.9 6.6 8.0 9.9 11.6 16.0
Torque (mg.)
2230 2260 2250 2200 2200 2200
Temperature (.degree.C.)
208 209 209 210 211 211
Plate Out Med-Hvy. Medium Light Slight
Very None
Slight
______________________________________
CONCLUSIONS
The recipe for Pellet A, Exp. E was used in the foamed composition in Table
13. The results are set forth therein. These results indicate that the
blend of an azodicarbonamide/bicarbonate produces a medium density foam
having thermal stability and improved impact resistance.
TABLE 13
__________________________________________________________________________
Blend 1
Blend 2
Blend 3
Blend 4
EXP. E
EXP. E
EXP. E
EXP. E
EXP. E
EXP. E
Pellet A Solid Foamed
Foamed
Foamed
Foamed
Foamed
EXP. E
__________________________________________________________________________
Pellet B Azodicarbonamide, %
1.09 0.88 0.65 0.43 0.22
Sodium Bicarbonate, % 0.06 0.12 0.18 0.24 0.30
DTS Test:
Time, min. 26.5 7.2 9.6 13.5 16.5 19.7 31.7
Torque, mg 2200 2200 2260 2210 2210 2210 2200
Temperature, .degree.C.
211 209 210 211 211 211 210
Plate-out sl. med. sl. sl. sl. sl-med.
clean
Density (actual)
1.486 0.79 0.79 0.79 0.76 0.74 0.94
Izod Impact, in.-lb./in.
1.7C 0.3C 0.4C 0.3C 0.3C 0.3C 0.5H-C
Tensile Strength
@ Yield, psi. 6660 2180 2120 2040 2010 2010 2500
@ Break, psi. 5620 2340 2260 2180 2130 2120 2500
Modulus, psi 326,000
121,000
121,000
117,000
112,000
114,000
140,000
% Elongation 15 34 32 27 25 20 13
Flexural Strength, psi.
12.715
4434 4361 4384 4136 4345 6146
Modulus, psi. 363,793
113,245
114,222
118,991
112,716
119,077
160,971
CTE, .times. 10.sup.-5 in/in C
__________________________________________________________________________
Table 14 set forth below investigates the use of different impact
modifiers. The standard tests, set forth with respect to Table 3, were
also carried out.
TABLE 14
__________________________________________________________________________
Pellet A EXP. E
EXP. F
EXP. G
EXP. H
EXP. I
EXP. J
__________________________________________________________________________
DTS Test:
Without CBA
Time, min. 29.2 34.6 33.6 30.3 19.0 22.3
Torque, mg 2300 2290 2400 2450 2450 2450
Temperature, .degree.C.
210 210 209 211 211 211
Plate-out none sl. sl. med. hvy. sl.-med.
3.5% CBA Pellet 5 (w/1.09%
Azodicarbonamide)
Time, min. 7.2 7.0 7.1 7.2 6.0 6.4
Torque, mg. 2280 2280 2320 2400 2380 2350
Temperature, .degree.C.
209 209 209 208 209 210
Plate-out med. med. med. med-hvy.
hvy. med-hvy.
1.94% CBA Pellet 6 (w/.30%
Exocerol 232)
Time, min. 27.7 30.8 27.3 26.3 20.4 20.2
Torque, mg 2370 2300 2320 2400 2400 2390
Temperature, .degree.C.
210 210 210 210 210 210
Plate-out none sl-med.
sl. sl. med. med.
Specific Gravity
1.486 1.507 1.457 1.491 1.481 1.479
Izod Impact 1.66C 2.09C 2.92C 2.27C 1.65C 1.24C
Vhit
Tensile Strength,
@ Break, psi.
6660 6660 6010 6620 7070 7370
@ Yield, psi.
5620 5910 5350 5880 6370 6420
Modulus, psi.
326,000
341,000
304,000
340,000
362,000
381,000
% Elongation 15 34 58 36 26 23
Flexural Strength, psi.
12,715
12,399
11,277
12,484
13,326
14,072
Modulus, psi.
363,793
357,152
335,775
363,006
398,483
412,281
__________________________________________________________________________
The results of Table 14 are set forth in the bar graph shown as FIG. 4.
These results illustrate that the blend of a azodicarbonamide and
bicarbonate blowing agent provides better overall results in terms of
stability and foaming as compared to just azodicarbonamide or bicarbonate
blowing agent alone. Furthermore, the acrylic impact modified compounds
were more thermally stable than those compounds modified with MBS or ABS.
Table 15 shows the properties of various foamed compounds. The target was
to achieve a foam density of about 0.75 to about 0.80.
TABLE 15
__________________________________________________________________________
Pellet A EXP. E EXP. E EXP. F EXP. F EXP. G EXP. G
Pellet B CBA Pellet 5
CBA Pellet 6
CBA Pellet 5
CBA Pellet 6
CBA Pellet 8
CBA Pellet
__________________________________________________________________________
6
% CBA used:
3.5 2.2 3.5 2.2 3.5 2.2
Rough Density
0.88 0.89 0.90 0.73 0.94 0.69
Density (actual)
0.85 0.78 0.88 0.71 0.93 0.66
Izod Impact, in.-lb./in.
0.3C 0.3C 0.3C 0.3C 0.3C 0.3C
Vhit, 3/8", in.lb./mil.
0.24/D 0.15/D 0.24/D 0.19/D 0.30/D 0.30/D
Tensile Strength
@ Yield, psi.
2270 2070 2290 1690 2670 1800
@ Break, psi.
2410 2100 2500 1810 2840 1870
Modulus, psi.
133,000
120,000
129,000
95,000 152,000
105,000
% Elongation
31 13 41 22 40 19
Flexural Strength, psi.
4906 3607 4630 3566 5556 3806
Modulus, psi.
125,750
99,859 125,310
102,248
144,165
108,582
% CBA used:
3.5 2.0 3.5 2.0 3.5 2.0
Rough Density
0.89 0.75 0.78 0.70 0.89 0.99
Density (actual)
0.89 0.74 0.76 0.70 0.84 0.90
Izod Impact, in.-lb./in.
0.3C 0.3C 0.3C 0.3C 0.3C 0.3C
Vhit, 3/8", in.lb./mil.
0.34/C 0.36/D 0.27/D 0.28/D 0.19/T 0.16/T
Tensile
@ Yield, psi.
2620 2090 2320 1990 2770 2660
@ Break, psi.
2740 2170 2460 2040 2800 2680
Modulus, psi.
149,000
117,000
136,000
115,000
170,000
158,000
% Elongation
37 26 33 19 17 13
Flexural Strength, psi.
5901 4904 4973 4598 4594 3999
Modulus, psi.
160,139
138,396
128,983
128,396
127,557
109,676
__________________________________________________________________________
The bar graph in FIG. 5 compares the VHIT results as in ASTM D4226 with a
3/8" diameter Hemispheric Impactor (tup) of various experiments as
designated therein to the following recipe in the U.S. patent application
No. 08/580,563 (Comparative Recipe).
______________________________________
Parts
______________________________________
Pellet A
TempRite 677 .times. 670 CPVC Resin
100
S-70 Tin Stabilizer 3.5
Thermolite 12 (Tin Dilaurate)
0.5
Paraloid K-400 (Acrylic Process Aid)
8.0
Paraloid K-175 (Acrylic Lubricant)
1.0
AC 629A (Oxidized Polyethylene Lubricant)
1.5
G-70 Beads 0.5
Glycoluble 674 Lubricant
0.5
Tioxide R-FC 6 (Titanium Dioxide)
4.0
Pellet B - CBA Pellet 1 3%
______________________________________
This Comparative Recipe compound has a profile density of 0.92.
The results in the bar graph of FIG. 5, indicate that using an impact
modifier with a foamable CPVC composition in a skinless profile will
generally in most instances result in a tougher, less penetrable profile
as compared to a compound not having the impact modifier. This appears to
occur whether an azodicarbonamide CBA system is used or whether a blend of
a azodicarbonamide and bicarbonate is used. Furthermore, irrespective of
the large density differences between the CBA used with Pellet A compound,
the impact values of the foam remain essentially constant.
A comparative example using PVC was performed. The PVC recipe is set forth
below in Experiment K.
______________________________________
EXP. K
______________________________________
103EP F76 PVC, 0.92 IV by Geon Company
100 parts
S-70 Dibutyl Tin Bis Isooctyl Thioglycolate Stabilizer
2.0
Witco-Polymer Additives Group, Mark 292 S
Goodrite 2301 .times. 36, Acrylic Processing Aid, Zeon Chemical
6.0
Kane Ace B-22 KO, MBS Impact Modifier, Kaneka
5.0
Calcium Stearate, 6 extra dense, Witco Chemical Co.
0.8
Acuwax, Ethyl Bis Stearamide, Lonza Inc.
0.8
Wax "E", Montan wax w/dihyric alcohol, Hoechst Celanese
0.4
Tioxide R-FC6, Titanium dioxide, Tioxide America, Inc.
5.0
______________________________________
The test results shown in bar graph form in FIG. 6. These results indicate
the PVC polymers (Exp. K) thermal stability is negatively affected by both
blowing agents. The sodium bicarbonate CBA catalyzes the degradation per
unit weight more dramatically than the azodicarbonamide CBA. The CPVC
polymer (Exp. D) without costabilizer has the thermal stability reduced by
the addition of an azodicarbonamide blowing agent but the sodium
bicarbonate blowing agent actually increases the stability beyond the
original unfoamed CPVC. The polymer in Experiment G acted the same as the
polymer in Experiment D with the following exceptions:
the azodicarbonamide CBA reduces the thermal stability of a co-stabilized
CPVC compound to the same level as a non-costabilized CPVC compound.
the sodium bicarbonate CBA actually provides more thermal stability to the
polymer than the original unfoamed CPVC compound with the costabilizer.
In summary, a novel and unobvious medium density CPVC foam has been
described as well as the process of forming such a foam. Although specific
embodiments and examples have been disclosed herein, it should be borne in
mind that these have been provided by way of explanation and illustration
and the present invention is not limited thereby. Certainly modifications
which are within the ordinary skill in the art are considered to lie
within the scope of this invention as defined by the following claims.
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